Reduction of 3,4,5-tris(methylthio)-1,2-dithiolium iodide (1) with sodium borohydride followed by oxidative work-up affords an isomeric mixture of the novel macrocycles 4,5,9,10-tetrakis(methylthio)-1,2,6,7-tetrathiacyclodeca-4,9-diene-3,8-dithione (6a) and 4,5,8,9-tetrakis(methylthio)-1,2,6,7-tetrathiacyclodeca-4,8-diene-3,10-dithione (6b).